Astro Hog

[Martyn K]

At the moment this is more of a planning blog. The plans arrived last week and I am planning a few changes. (as you do) Hopefully ths wont spoil the flavour or sprit of the build.

 

So far, the changes planned are:

 

1. A lot less dihederal - reduced from 4 5/8" to about 1 1/2" total

2. A built up fin and rudder. the original is only 3/32 sheet balsa. I'll probably move to somthing about 1/4" thick but built up with a simplified hinge arrangement as well

3. Discard the rear wheel brake.

4. Aileron servos in the wings

5. ASP 61 engine (just bought s/h off Fleabay) side mounted with the silencer (none fitted on the original ) hanging underneath. I'll also use a commercial nylon engine mount.

6. Simplified Aileron hinges.

 

That's about it for now. I photocopied all the formers during the week and cutting will probably start this weekend.

 

Progess will be slow as I currently have the "Ohm Maiden" on the building board with at least another 3 weeks work before I can free up significant space to build

 

Regards

 

Martyn

 

 

 

[Biggles' Elder Brother - Moderator]

Oh, I dunno - (sucks in breath) - I think that within the rules the rear wheel brake is an essentail element

 

It would be good fun watching you try to use it anyway!

 

BEB

[Martyn K]

I have to admit - I spent an hour an hour looking at the plan trying to work out what the hell it was. intriguing - it works from the throttle 'actuator' - when the throttle is shut, it jams a rod into the rear tyre!

 

M

[IanN]

We DEFINITELY want to see that working

[Martyn K]

Is this peer pressure? No - I don't want to do it.

Ok I'll do it.

 

Watch this space

 

M

[kc]

Presumably a standard size Astro Hog?

The Sig website shows the instruction manual online and says they have reduced the dihedral from 8 inches under each wing to 6 inches each wing. Total 12 inches. A bit different to your plan?

Sig also say they fit strip ailerons because less slop etc.

[Martyn K]

Hi KC

 

Yep - standard 1957 vintage. Wing dihederal definitely says 4 5/8" under each wing tip. This equates to 9 1/4" total. It certainly looks a lot. I was tempted to do for a flat wing, but I'll see what it looks like with 1.5 or 2" under each tip.

 

OK on the ailerons. The hinging on the original is quite complex, they have emulated the hinge mechanism of a full size aeroplane. I'll get rid of the slop using modern hinges and a dedicated servo for each aileron.

 

I was tempted to try flaps as well but that may be pushing the vintage bit too much.

 

Martyn

[Martyn K]

PS - that was your 1000'th post. Do you get a medal or a promotion?

 

1000 forum posts

Presumably a standard size Astro Hog? The Sig website shows the instruction manual online and says they have reduced the dihedral from 8 inches under each wing to 6 inches each wing. Total 12 inches. A bit different to your plan? Sig also say they fit strip ailerons because less slop etc.

 

Martyn

[kc]

1000? he cannot mean me? Yes, he did!

 A medal? I think I have rocked the boat too much for that! ( it's Mods v Rockers)

 

I have just looked up the Astro Hog 40 article from Radio Modeller Jan 85 ( an 82 percent version )and this comments on the original size having "a reasonable dihedral to maintain some lateral stability" but no measurements are given.

It is possible you have the British plan which was a later amendment to the original. (just a guess, I dont know )

Really we should be talking about the angle as the 4 5/8 is not much on such a large span.The angle in the 3 view in RM is about 18 degrees total!  ( 9 degrees each side )But who knows if the 3 view is accurate.

 

I would be tempted to use 4 5/8 and say it's original at least.     I would say its likely the Sig website is a misprint and they meant 8 total not each tip   ( 4 5/8 doubled roughly )

 

If you read throgh the Sig instructions you can see it says "  The angle of the gauge is 6 deg., half of the total dihedral amount (12 deg.) of the finished wing. "

Edited By kc on 04/11/2011 15:59:56

Edited By kc on 04/11/2011 16:06:30

[Martyn K]

Hi kc

 

I think this photo shows the original:

I am aiming for something more like this:

 

 

With all that fuselage side area, it wont be lacking any lateral stability

Martyn

Edited By Martyn K on 04/11/2011 16:26:52

[kc]

Reading right through the Sig website it says anything between 3 to 3 1/4 inch each side.

 

Looks nice and somewhat like a Spacewalker when flatter  in your photo but how did it fly ?

Its your choice, your model!

Edited By kc on 04/11/2011 16:29:23

[Martyn K]

Hi kc,

 

I'll risk it with less dihederal. Remember back in the 50's when it was designed it wasn't proportional R/C as we know it now, it was "bang bang" (I think that is what it was called) so more neutral stability was essential. I want it to behave like a low wing trainer rather than a high wing trainer.

 

Martyn

[Martyn K]

Posted by kc on 04/11/2011 15:42:52:

 

If you read throgh the Sig instructions you can see it says " The angle of the gauge is 6 deg., half of the total dihedral amount (12 deg.) of the finished wing. "

I have just checked the plan and it actually states 16 degrees (total) dihederal so I presume that this is original. It looks very excessive.

 

Martyn

[Martyn K]

I have cut out all the formers for the fuselage. I photocopied the relevant bits onto A3 paper (checking that they are the correct size - some copiers actually 'shrink' the copy be a few per cent...

 

Cut out the outline, then I used a light dusting of 3M photo mount to glue them down onto the ply. (I have decided to use liteply instead of balsa where balsa was specified.

 

 

A couple of hours with a bandsaw and a tile saw (I use a tile saw for cutting the holes out of formers - it doesn't tear the wood like a fret saw does) and hey presto! (or even voila!)

 

and

The paper simply peels off the wood. Any residue glue can be removed with a little solvent.

 

Lots more to come...

Edited By Martyn K on 07/11/2011 20:05:09

[kc]

There is a comment on RCuniverse which states there are both high and low tailplane positions on an Astro Hog. Your photos appear to show 2 different versions or is it an illusion? Which are you building?

[Martyn K]

Hi kc

 

I hadn't spotted that. The plan version is elastic banded on low tailplane. I'll keep with the plan but probably make it permanent.

 

I'll have a google round. It's quite clear that there are lots of variants of the 'hog around.

 

Martyn

Edited By Martyn K on 09/11/2011 13:20:46

[Martyn K]

It looks like SIG have redesigned the back end somewhat for their kit. Struggling to find a build blog for the plan version.

 

(edited) Apparently the 'hog was redesigned back in '83 with several changes and improvements. This plan drawing shows the low tail, no wheel brake and a 3/16" fin and rudder.

 

My plan has a 3/32" fin and rudder which is clearly on the skinny side hence my decision to make a built up one.

 

 

Martyn

Edited By Martyn K on 09/11/2011 14:15:45

[fly boy3]

Many years ago I built an AH from the David Boddington plan, and it flew extremely well. I reduced the dihedral to about 11/2 inches under each wing tip. After all it is supposed to be an airobatic job. Cannot remember the exact weight, but it was well over a pound lighter than the equivelant Sig model at the time. Another forum reckons it is the best flier of all time ! Cheers

[Martyn K]

Thanks for that fb3. I am looking forward to making a reeal start on it shortly. Apart from the dihederal, it actually looks (construction wise) about 20 years ahead of its time

 

Martyn

[Sparks]

Hi Martyn,

 

The consensus of opinion from various groups is that a total dihedral angle of 6 deg is a good compromise these days.

 

Hope you will use the barn door ailerons and taildragger u/c, not the Sig narrow ailerons and trike u/c - it wouldn't look like a 'Hog otherwise. We'll let you off using the valve receiver as shown on the original Fred Dunn plan.

 

Cheers, Daredevil Dudley - Hog pilot

 

[Martyn K]

Thanks Sparks

 

I have been looking around for valves that will work at 2.4Ghz and I have found 2. The next problem is generating the 600V DC for the Anode

 

Seriously though, I will be using the 3D sized ailerons plus a tail dragger plus the rear wheel brake. I may go for a 3/16" sheet fin and rudder now that the typo on my plan has been identified.

 

I was also going to have a flying pig pilot but you have beaten me to it...

 

Martyn

Edited By Martyn K on 09/11/2011 18:05:27

[kc]

I wonder if the 3/32 is really a misprint or whether the intention was to have 2 layers of 3/32 with the joints ( or grain ) staggered making a total of 3/16 ? I have seen this on other older designs.

 

( sorry if I keep posting problems for you! )

[Martyn K]

Hi kc

 

not posting problems - actually making me think about it. I'll need to go and check. I have to admin that 3/32" for a fin seemed to be stoopidly thin on a model this size - laminating up would be a sensible approach and I agree would add a lot of stiffness and warp resistance.

 

Thanks for that.. I'll check

 

Martyn

[Sparks]

Martyn,

 

The original AMP Fred Dunn article (April 1958) and subsequent re-drawn plans by Berkely Models and William R. Miller (2004) all specify 3/16" Fin and Rudder.

 

Sparks (Hogaholic)

[Martyn K]

I've checked the plan tonight. It definitely say 3/32" fin and rudder. However, the plan view shows the thickness as 3/16" measured.. I still put it down as a typo.

Thanks for the clarification.

Martyn